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Homework Help: Arc Length

  1. Sep 9, 2005 #1
    Hello, I was wondering if someone could check and see that i did this problem right. You need to find the arc length of the vector from t=0 to 1:

    r= <2e^t,e^-t,2t>

    So first i took the derivative and got velocity.

    v=<2e^t,-e^-t,2>

    Next i used the formula for arc length.

    arc length = Integral from 0 to 1 of the norm of velocity.

    The answer i got was 2e+e^(-1)-3

    I am not sure if I am doing my integral right. I'd appreciate to see if someone gets the same answer that I do or tells me if i made a mistake somewhere.
    Thanks!
     
  2. jcsd
  3. Sep 10, 2005 #2

    CarlB

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    Homework Helper

    I got a different answer. If I'm right and you're wrong, it's because [tex]\int e^{-t} = -e^{-t}[/tex], not [tex]\int e^{-t} = +e^{-t}[/tex]. But it's also quite possible that I didn't get the right answer for some other reason.

    Anyway, check your work and look for a sign error associated with an integral of [tex]e^{-x}[/tex]. And good luck.

    Carl
     
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